Sharpening drill bits.

[Andyvon]

Does anyone have a straightforward method for sharpening small diameter HSS twist drill bits please?

I've just bought quite a few new drill bits - tungsten coated, cobalt and HSS. However, that leaves me with several dozen old small diameter HSS drill bits that would be fine after being sharpened. The drills range in diameter from about 1mm to 5 or 6mm. My old Martek drill sharpener has given up and I was never happy with it anyway. The 'Drill Doctor' is too much money. When I ask around the shops about sharpening the general thinking seems to be that drill bits are so cheap they can just be thrown away. Well, my new drill bits weren't that cheap and I feel quite reluctant to throw all my old ones away if there is a fairly easy way to resurrect them.

Has anyone else come across this before and found an answer? Thanks in anticipation.

[scotman]

Hi

Like you I have been looking for a reasonable home sharpener for some time. I have to say that it is probably true that small sizes are not now economic to resharpen.
A 'proper' drill sharpening machine can cost from several hundred pounds up to several thousand and, from what I have seen, attempts to produce cheaper versions have not been very good.
Even the better ones hardly ever say they can do drills less than 3mm.

This looks good

http://www.novatechon...roducts/mega/mega.htm

I have subscribed to this in case anyone else can provide an answer for us both.

[Andyvon]

Hi Scotsman.

Wow - that's the business! As you say, all the good drill sharpeners are expensive. They might be fine for workshops where they pay for themselves but not for the average person like you or me. I've had some success sharpening larger HSS drill bits with an oil stone but it took quite a time to get a sharp drill that worked well. It's certainly not practical for the smaller ones. I'll hang on to my old drills for a while in the hope there is an answer.

[scotman]

I think it is just down to economics. Drill costs £1, time to set up and sharpen = 6mins @ £15/hour + amortised cost of machine and it doesn't add up. Cheaper to throw away unless you don't charge for the time taken.

[Andyvon]

True Scotsman. But I look at all my drills and the thought of throwing them all away...............!

[heathfield]

Wow! That drill grinder is the business, all right! But for me, with smaller bits, replacement is the answer. And bear in mind - using the correct type of bit for the job, and using it with care and consideration for both the bit and the material you're drilling can greatly increase its lifespan.

[scotman]

Heathfield, I agree with you about use. Also, buying quality products in the first place. I tend not to throw mine away, I keep thinking that's good steel, I'll make something else out of it. Never seem to get round to it though.

[heathfield]

Scotman, if you can figure out a use for worn-out drill bits, (apart from my using them as drift pins), then please let us all know!!

[Andyvon]

Keeping the drill at a fairly slow speed is important too, as can be the use of a lubricant.

[alavahalf]

How do you manage to drill at a slow speed with small diameter drill bits (1 - 6mm)without snapping them ..?

[scotman]

Heathfield

Trust me, when I figure out something to do with old drills I shall post it here first.

[Andyvon]

By setting the power drill to a low speed and being careful Alavahalf. Also starting a small hole with a hand drill then progressing to a power drill with larger bits. Drilling at high revs is a sure way of blunting the drill bit in seconds as the metal overheats and loses temper.

[chattykathy]

My OH, who is a toolmaker, says to use a cheap bench grinder. He reckons you could get one for about £25

[scotman]

Using bench grinder requires more skill than I possess.

[beso]

I have a sharpening jig that works well with a bench grinder on large bits. Small ones I sharpen freehand using much the same principles as the jig. If you understand how cutting edges work it isn't too hard to get a quite reasonable shape.

Obviously you need to get the angle correct but this can be judged by the angle of the bit to the wheel. It needs to be symmetrical and this is done by simply rotating the bit.

The other key factor is the relief behind the cutting edge. Take a good look at a new bit and notice the few degrees slope behind the cutting edge. You are probably aware of it since you have sharpened bits on an oil stone. This is the hardest part for any jig or automatic sharpener to reproduce and is probably the most important aspect so long as the angle and symmetry are not ridiculously wrong.

Bits sharpened like this may not be ideal for precision work but there are many times when they will do the job.

I even resharpen the snapped off ones like this. They are very handy when doing a job where they are at risk of being snapped again and you don't want to risk a new one. Since they are shorter they are less likely to break too.

[Andyvon]

Thanks Kathy and Beso. I used to have a bench grinder which I sharpened larger drills on but I don't really have anywhere to mount one now.

Beso - I know about the angles such as 59 degrees and the relief angle on the sides. There are several very good American instructional videos on YouTube that show that. After much practise I do manage to get reasonable results with an oil stone but it's so time-consuming. Perhaps I should invest in a bench grinder with a very fine stone.

Thanks everyone.